In a typical v-twin engine having a dry-sump design, motor oil is pumped out of the crankcase as quickly as possible to a remotely mounted oil tank once the oil has circulated to all of the components inside the engine. The crankcase always contains some oil that is in the process of making its way to the return side of the oil pump, and some of the oil collects in the bottom of the crankcase, and some of the oil saturates the air inside the crankcase.
Magnetic sensing of the crankshaft position can be used to properly regulate fuel feed and spark timing, and the magnetic sensing can be accomplished by machining index marks into the flywheels, for example in a way that resembles paddles around a paddle wheel. Then the position of the crankshaft is determined with an electronic sensor mounted perpendicular to the crankshaft.
Such “paddles” that are cut into a flywheel will contribute to “frothing” within the crankcase. This frothing of the motor oil inside the engine has two major downsides: first, it slows the return of motor oil to the external oil tank because the oil pump cannot pump foam as quickly as it can pump liquid; and second, it creates more super-saturated mist that must be separated back into its air and oil components before allowing that air to leave the engine through its crankcase breathing system.
As seen in FIG. 1, typical prior art flywheels 23 and 24 are connected by a pin, which fits into the hole 28. The pin drives the pistons 70 and 80. When the crankshaft 30 rotates, then so will the flywheels. The flywheel 24 has teeth 40 which allow an electronic sensor 50 to monitor the motion of the flywheel. Note that the support element 52 is substantially perpendicular to the crankshaft 30. The large gap 60 typically covers an angle of thirty degrees, and this gap allows the sensor 50 to ascertain the angular position of the flywheel 24 not only when it senses the gap, but also when it senses that a particular number of teeth have passed by since the gap was sensed.
The prior art patent to Lodise (U.S. Pat. No. 6,499,341) is incorporated by reference herein. Lodise discloses a crank gear with a crankshaft passing through its center. The crank gear has paddles or “teeth,” and a sensor detects the paddles as they pass by the sensor. The sensor waits until an indicator on the crank gear passes by, and then the sensor begins counting groups of paddles, and accordingly regulates fuel feed and/or spark timing based upon how many paddles have passed by the sensor. Unfortunately, this type of paddle arrangement can create frothing of the motor oil, with the resulting difficulties described above.
There are various other existing patents for flywheels, but they do not solve these problems. Thomsen (U.S. Pat. No. 6,663,789) discloses a flywheel, including a timing mark that projects from the side of the flywheel. The timing mark is alternatively a depression, such as a machined slot or void in the side of the flywheel, and a sensor detects the timing mark as it passes by. However, the Thomsen apparatus is unable to measure the rotational speed of the crankshaft at selected angular positions of the crankshaft, and those measurements are very useful for regulating fuel feed and/or spark timing.
Neither the timing mark of Thomsen nor the indicator of Lodise will cause frothing of oil. However, such frothing is caused by the paddles of Lodise, and Thomsen does not provide any components that provide the useful function performed by the paddles of Lodise.
Another relevant prior art patent is Weber (U.S. Pat. No. 6,131,547). Weber discloses a “tone wheel” which has sidewall cavities that penetrate through the wheel. Passage of the tone wheel past a sensor allows electromagnetic determination of the engine's angular position and rotational speed. However, the tone wheel of Weber is located within a gear having radial teeth, which would potentially cause frothing in a crankcase.
Bowling (U.S. Pat. No. 6,575,134) discloses a flywheel having a substantially smooth rim, and three holes in the sidewall that extend through the sidewall from one side to the other. However, Bowling does not employ those holes for monitoring motion of the flywheel. Instead, various magnets are attached to the flywheel, some of which may be attached to a sidewall of the flywheel. The magnets, rather than the three holes in the flywheel, allow the position to be sensed.
Saker (U.S. Pat. No. 6,164,159) discloses a flywheel having a smooth rim, but Saker does not disclose a sensor. The recesses and openings in the sidewall of Saker's flywheel are for receiving pins, shafts, or the like, rather than for monitoring motion of the flywheel.
Stadelmann (U.S. Pat. No. 4,235,101) discloses a “sense wheel” mounted adjacent to a flywheel. The flywheel has a smooth rim, and the flywheel also has cavities extending from one sidewall of the flywheel through to the other sidewall of the flywheel, for receiving bolts and the like. Stadelmann discloses that a sidewall of the sense wheel (rather than the flywheel) has holes, slots, indentations, protrusions, and the like, wherein as each sense feature passes near a sensor it is magnetically detected. Stadelmann mentions that these sense features could be implemented on a flange of the crankshaft.